RESULTS: Thomas Reh, at the University of Washington in Seattle, and his team have developed a reliable way to generate cells known as retinal progenitors, which have the ability to turn into any of the cell types found in the retina, such as photoreceptors or retinal ganglion cells. Preliminary results show that when the cells are transplanted into retinas either in a dish or in live lab animals, the cells migrate to different layers of the retina and begin to express proteins characteristic of the neighboring cells–including photo­receptors, which convert light into electrical signals.

WHY IT MATTERS: In retinitis pigmentosa and age-related macular degenera­tion, photoreceptors degenerate over time, leading to loss of vision. Previous research showed that these diseases can be treated by replacing lost cells, but there was no reliable source of replacements.

METHODS: Researchers exposed human embryonic stem cells to a mix of three proteins, called growth factors, that are involved in the development of head and eye tissue. The treated stem cells developed into retinal progenitors.

NEXT STEPS: The researchers will examine whether the cells actually restore vision when transplanted into the eye.